From 315562c9af3d583502b35c4b223a08d95ce69864 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Mon, 7 Sep 2020 15:15:44 +0200 Subject: x86/sev-es: Adjust #VC IST Stack on entering NMI handler When an NMI hits in the #VC handler entry code before it has switched to another stack, any subsequent #VC exception in the NMI code-path will overwrite the interrupted #VC handler's stack. Make sure this doesn't happen by explicitly adjusting the #VC IST entry in the NMI handler for the time it can cause #VC exceptions. [ bp: Touchups, spelling fixes. ] Signed-off-by: Joerg Roedel Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20200907131613.12703-44-joro@8bytes.org --- arch/x86/kernel/nmi.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/x86/kernel/nmi.c') diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index 4fc9954a9560..4c89c4d3cb82 100644 --- a/arch/x86/kernel/nmi.c +++ b/arch/x86/kernel/nmi.c @@ -33,6 +33,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include @@ -488,6 +489,12 @@ DEFINE_IDTENTRY_RAW(exc_nmi) this_cpu_write(nmi_cr2, read_cr2()); nmi_restart: + /* + * Needs to happen before DR7 is accessed, because the hypervisor can + * intercept DR7 reads/writes, turning those into #VC exceptions. + */ + sev_es_ist_enter(regs); + this_cpu_write(nmi_dr7, local_db_save()); irq_state = idtentry_enter_nmi(regs); @@ -501,6 +508,8 @@ nmi_restart: local_db_restore(this_cpu_read(nmi_dr7)); + sev_es_ist_exit(); + if (unlikely(this_cpu_read(nmi_cr2) != read_cr2())) write_cr2(this_cpu_read(nmi_cr2)); if (this_cpu_dec_return(nmi_state)) -- cgit v1.2.3 From 4ca68e023b11e4d5908bf9ee326fab01111d77d5 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Mon, 7 Sep 2020 15:16:11 +0200 Subject: x86/sev-es: Handle NMI State When running under SEV-ES, the kernel has to tell the hypervisor when to open the NMI window again after an NMI was injected. This is done with an NMI-complete message to the hypervisor. Add code to the kernel's NMI handler to send this message right at the beginning of do_nmi(). This always allows nesting NMIs. [ bp: Mark __sev_es_nmi_complete() noinstr: vmlinux.o: warning: objtool: exc_nmi()+0x17: call to __sev_es_nmi_complete() leaves .noinstr.text section While at it, use __pa_nodebug() for the same reason due to CONFIG_DEBUG_VIRTUAL=y: vmlinux.o: warning: objtool: __sev_es_nmi_complete()+0xd9: call to __phys_addr() leaves .noinstr.text section ] Signed-off-by: Joerg Roedel Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20200907131613.12703-71-joro@8bytes.org --- arch/x86/kernel/nmi.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'arch/x86/kernel/nmi.c') diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index 4c89c4d3cb82..56b64d779856 100644 --- a/arch/x86/kernel/nmi.c +++ b/arch/x86/kernel/nmi.c @@ -478,6 +478,12 @@ DEFINE_IDTENTRY_RAW(exc_nmi) { bool irq_state; + /* + * Re-enable NMIs right here when running as an SEV-ES guest. This might + * cause nested NMIs, but those can be handled safely. + */ + sev_es_nmi_complete(); + if (IS_ENABLED(CONFIG_SMP) && arch_cpu_is_offline(smp_processor_id())) return; -- cgit v1.2.3